Question about Quantum Mechanics?

Question

Firstly, please forgive my ignorance on Physics in general, I am not well versed in this area.

I read that scientists performed an experiment where they fired a photon through two slits, and expected it to go through one of them. When the scientists were not observing the photon, it passed through both slits, but when they observed it, it passed through only one. This led to the conclusion that perceiving something holds the power to change it, confirming Neil Bohr's school of thought while disproving Einsteins, who felt that their was a missing equation in Quantum Mechanics.

Even Steven Hawkins said something about how simply looking at the universe potentially affects how the our universe was created or something like that.

So my question is, does perceiving something really change the underlying nature of something? If something is not perceived, then is it in a state of flux. Isn't this sort of like the Schrodinger's Cat though experiment, where if you don't perceive the cat, it is in a state of flux between living and dead?

I honestly have to agree with Einstein on this one, it sounds absurd!? Its ridiculous to assume that simply the perception of a living organism can alter the motion of a photon, or that if a tree falls in a forest then it doesn't make any sound if it is not heard. By this assumption, can I say that if my mother were to die tomorrow in a vacuum, in which she was not-perceived by anyone nor did her carcass interact with anything, then theoretically my mother is in a limbo state of flux between living and dead? My mother can remain in a state of quasi-immortality as long as she is not perceived/interacted with.

Well? Is this true? Can someone help me here?

Answer 1

Where to begin ...

Your history is wrong.



This was not the experiment that was used to justify QM. Einstein knew plenty about it and didn't at all believe that it disproved his idea of hidden variables (not equations). It wasn't until much much later that a man named Bell (not the telephone guy) showed that it was impossible to explain all of the things observed with local hidden variables.



The double slit experiment has never actually been done with single photons. It has been done with single electrons. We, of course, get the same basic result, but photons is much much harder to do.



Schrodinger's cat is a thought experiment by Schrodinger to show that the Copenhagen interpretation of QM is absurd. If you think that SC is crazy, then you are thinking exactly what Schrodinger wanted you to think.



Furthermore, SC wasn't just, you put a cat in a box and it is now neither alive or dead until you observe it. S linked the life of the cat to the decay of some radioactive material. He pointed out that since this was not in a state until you observed it, the cat would be neither alive nor dead until you observed it. The actual presence of the decaying nucleus is really really important to the thought experiment.



If you don't know what the Copenhagen interpretation of QM is, there really isn't a point in talking about SC since the entire purpose of it is to try to show that the CI is silly.



Also, there is no requirement for a living organism. Observer doesn't mean a living thing. It doesn't mean a person. In the experiment you mentioned, the observer is the piece of equipment that was used to make the measurement of the photon. It might be a screen that flashes when it is hit by a photon or a photo-voltaic cell, or something else, but it is not alive.



Now, let us talk about the actual science.

Let's say you were in some body of water. The ocean, a swimming pool, whatever. And you build a wall. In this wall, you cut out some sections, so that you would basically have slits (like in the double slit experiment, but much bigger). Then you had a wave approach the wall. Which slit would the wave pass through? Well it would pass through both of them of course, this is easy to test and verify and you should probably already know this.



This is what we should expect when we say that light is a wave. Like the water wave, when it hits the it passes through both slits. But when it reaches our detector, which we put a ways away from the slits, the photon (electron, proton, neutron, etc) will only be detected in one place. This is called wave particle duality. Basically it means that in certain situations objects behave like waves and in other situations they behave like particles. Some objects, a car for instance, behave like particles quite a bit of the time. Other objects, light for instance, behaves likes waves a lot of the time.



And here is the kicker, observing it can change if it behaves like a particle or a wave. For instance, when the light interacts with the slits, it behaves like a wave. When it interacts with the PV cell (who is the observer in this case) that we are using to measure it, the photon behaves like a particle.



If we much the PV cell (the observer) very closer to the slit, so that they are observing the photon right there, then we are casing the photon to behave like a particle, so now, like a particle it will pass through only one slit.



So, yes, by observing something we (PV cells, the rods and cones in our eye, other subatomic particle, anything that can interact with anything else) change the nature of something. But not really in the way you seem to think.

Answer 2

It is exactly Schrodinger's Cat.



People read way too into this one... There's nothing about "us choosing" or "consciousness" that determines the outcome of events. It is the *interaction* of reality with itself that determines the outcome. I.e. it's not someone looking at the electron, it is a detector that the electron interacts with, an inanimate object.



There's a lot of quirky things about quantum effects, which appears to apply to small things. For example, the beam of electrons in an old TV--you may know the momentum of these electrons, but their position is smeared across the entire length of the beam . . . once they hit the screen, we know their position, but not their momentum . . .



But a cat is way too big to enter into this quasiland of microscopic independence. A cat's molecules never even for a single moment have much time not interacting with something else or the cat's other atoms. It's a classical object. If all you have knowledge of is a quantum state that tells you 50% dead cat 50% live cat, that's just telling you that the odds are even that there is a dead cat in there.



At its heart, quantum mechanics is probability.



That means you don't know if the cat's alive or dead until you look. Obviously. But it's also obvious that by the time you do, the cat will have been dead or not already.



To answer your last question, what you are saying is also obvious. Don't you agree that if you don't hear anything from or about your mother . . . that you won't know if she's living or dead?



....................................................................................



"True, I won't know whether she is alive or dead or not, but that doesn't change the fact that she is either living or dead. Whether I know it or not does not affect her situation"



Never said it did.



I argued that any macroscopic entity, save for Bose-Einstein condensates, aren't going to exhibit behavior associated with non-interacting quantum particles.



"and it doesn't really seem like common sense that the interaction of something is going to change a photons action"



Of course it is. Don't you normally change the action of things by interacting with them?



"It will not go flying around through every possible flight path at the same time when I am not looking at it! But this is exactly what the photon is doing. Frankly its incredible! It takes a real stretch of the imagination for me to imagine that happening."



Well, this is just a conceptualization. It's just as accurate to say the photon isn't going along any of the paths. This viewpoint makes more sense when you look at quantum tunneling.



I'll also note that the Copenhagen interpretation is the most widely-accepted specific interpretation of quantum mechanics . . .



You might also be interested in checking out the EPR Paradox and Bell's inequality.



http://en.wikipedia.org/wiki/EPR_paradox



http://en.wikipedia.org/wiki/Bell's_theorem

Answer 3

hi Nuff; i for my section experience, with actual no scientific information, that each and each selection we make on a daily basis provides an possibility for yet another ( or parallel universe). I join the Robert A. Heinlein concept, in all probability previously some time yet, a great fiction author. attempt "The sort of The Beast" or "Stranger In an unusual Land"good easy exciting reads. yet time is a extreme venture, and one i'm afraid I even have very fastened notions upon. As i think God created it,and holds it until, as you ought to assert the time is nice, and guy ought to pass forward in common terms, residing each and each 2nd to the fullest, as there is not any going back. "The previous is historic past, the destiny a secret, we are able to in common terms stay interior the now." yet to punch a hollow into yet another universe, will in all probability take place at some point, what occurs next? nicely which would be an entire different universe back. LOL have exciting with this one! Bob